Question

A structural steel has an allowable stress of 21,600 psi. Express this in Pascal and MPa.

Answer 1

To solve this problem we will apply the conversion concepts given for the available units. Recall that the unit 'psi' is the expression equivalent to pounds per square inch applied on a surface. The force pounds in Newtons (mass per acceleration) are equivalent to

`1lb = 0.45kg*9.8m/s^2`

While square inches to square meters are equivalent to

`1 in^2 = 0.00064516m^2`

Making the conversion for the elimination of the units we would have

`\sigma = 21600psi`

`\sigma = 21600(lb)/(in^2)`

`\sigma = 21600(lb)/(in^2)((0.45kg*9.8m/s^2)/(1lb))((1in^2)/(0.00064516m^2 ))`

`\Rightarrow \therefore \mathbf{\sigma = 147647095.3Pa}`

`\Rightarrow \therefore \mathbf{\sigma = 147.64Mpa}`